1. Field of the Invention
The present invention relates to a fluorescent lamp capable of cleaning air, and more particularly, to a fluorescent lamp coated with nano-crystalline anatase TiO2 sol, which is a photocatalytic material acting as fluorescent agent, which is capable of increasing brightness of the fluorescent lamp when it is turned on.
The present invention also discloses a method comprising the steps of preparing semiconductor nano-crystalline anatase TiO2 solution using titanium alkoxide Ti(OR)4 as a main component in combination with chelating agents and than hydrolysis in aqueous solution, which semiconductor nano-crystalline anatase TiO2 solution is then coated onto surface of a fluorescent lamp tube. The fluorescent lamp tube coated with the semiconductor nano-crystalline anatase TiO2 solution is then baked to form a photocatalytic coating fluorescent lamp capable of cleaning air. The baking step is carried out at a low temperature in a range of 100-250° C. The fluorescent lamp comprises straight type tubes, annular shaped tubes, U-shaped tubes, spiral-shaped tubes, and special dual layer tubes.
2. Description of the Related Art
Photocatalysts have been developed for treating waste gases for the past few years, such as those described in, for example, Gregory B. Roupp & Lynette A. Dibble, Arizona State University, U.S. Pat. No. 5,045,288; Jeffrey G Sczechowski et al., The University of Colorado, U.S. Pat. No. 5,439,652; William A. Jacoby & Daniel M. Blake, U.S. Pat. No. 5,449,443; Zhenyu Zhang & James R. Gehlner, Inrad., U.S. Pat. No. 5,468,699; and Franz D. Oeste & Olga Dietrich Neeleye, U.S. Pat. No. 5,480,524.
The above-mentioned patents relate to treatment of waste gases, and were basically carried out in a hermetically sealed reactor. Utilization or operation of granular photocatalysts or photocatalysts coating granules therefore usually needs, in general, complex equipment to handle.
The above-described prior art examples have disadvantages making the prior art photocatalysts difficult to apply in the field of air pollutant treatment for a living environment. Of them, one waste water and/or waste gases disposal photocatalytic reactor comprising a UV lamp inserted into matrix with photocatalysts coated fibers, thereof is described in Michael K. Robertson & Robert G Henderson, Nutech Energy Systems Inc., U.S. Pat. No. 4,982,712. As mentioned above, such a reactor was a closed type one such that counter-flow of gases must be forced by a blower that makes such a reaction system impractical when used in living environments.
UV lamp treatment for waste gases is generally based on the sustained oxidative degradation against organic and/or inorganic hazardous materials in the air by a photocatalytic reaction to render them into non-harmful substances such as water or carbon dioxide. For example, U.S. Pat. Nos. 6,135,838 and 6,336,998, which are owned by the applicants of the present application, all describe such a UV lamp. Since the UV lamp is not a commercially available lighting apparatus, some research has focused on a commercial fluorescent lamp having a photocatalytic coating for cleaning air.
Hiroshi Taoda and Watanabe, U.S. Pat. Nos. 5,650,126 and 5,670,206, discloses a fluorescent lamp coated with titanium dioxide sol, than baked to 350-500° C., for deodorized the air. And the U.S. Pat. No. 6,024,929 by Ichikawa Shinichi, Furukawa Yashinori, and Azuhata Shigeru discloses a light-transmissive and transparent film photocatalyst made of anatase-type titanium dioxide and alpha type iron oxide formed on an outside surface of a glass tube used for a fluorescent lamp. The thin film photocatalyst is formed by sol-gel coating. But the temperature for baking the solution adhered to the outside wall of the glass tube is in a range of 450-600° C. when forming the thin film anatase-type titanium dioxide and is in a range of 560-770° C. when forming the alpha iron oxide α-Fe2O3. By baking the solution at so high temperature in the above-mentioned ranges, which made the coating too dense to work with high efficiency in photocatalysis for air cleaning.
U.S. Pat. No. 6,242,862 by Akira Kawakatsu and Kanagawa-ken discloses a photocatalytic membrane on a lamp with lighting fixture. The membrane is formed using TiO2 anatase particle dispersed liquid coating with a ground layer. The ground layer made of a metallic oxide : such as silane coupling agent, SiO2 sol, TiO2 sol, or Al2O3 sol, also with multi-layer structure provided lot of penetrating holes for increase the photocatalytic efficiency. However, the anatase TiO2 particles are obtained from a high temperature sinter process. Although the TiO2 Anatase particles are dispersed in an alcohol solvent, the hydroxyl groups on the particle surfaces are still at a low level, resulting in poor adhesion to the fluorescent lamp. For this reason, inorganic materials for enhancing adhesion such as silane coupling agent, SiO2 sol, TiO2 sol, or Al2O3 sol is needed. This inorganic materials distributed in lower the photocatalytic effect and lower the air cleaning efficiency, too.